Method for removing volatile impurities from raw oil by scrubbing and distillation with a stripping gas

ABSTRACT

A method of purification of liquid raw oil containing volatilizable impurities in which the raw oil is first fed into a scrubbing zone and from there into two subsequent purification zones, in one of which the impurities are volatilized and the volatilized impurities are passed into the scrubbing zone to be scrubbed with the fresh raw oil fed thereinto so that the latter will absorb the impurities and the raw oil thus containing an increased percentage of impurities is subjected in the other purification zone to purification in which at least a part of the impurities are removed by neutralization or distillation.

ilnite States Inventor Wolfgang Kehse Berlin, Germany Appl. No. 884,776

Filed Dec. 24, 1969 Patented Jan. 11, 1972 Assignee Fried, Krupp GmbHEssen, Germany Continuation of application Ser. No. 524,405, Feb. 2,1966, now abandoned. This application Dec. 24, 1969, Ser. No. 884,776

METHOD FOR REMOVING VOLATILE IMPURXTIES FROM RAW 01L BY SCRUBIBHNG ANDDlSTlLLATlON WITH A STRIPPING GAS 16 Claims, 3 Drawing Figs.

11.8. CI 203/42, 203/37, 203/80, 203/79, 203/87, 203/92, 202/183,260/428 lint. C1 B01d 3/38, BOid 3/10 Field of Search 203/42, 49,

Primary Examiner-Wilbur L. Bascomb, Jr. AttarneySpencer & Kaye ABSTRACT:A method of purification of liquid raw oil containing volatilizableimpurities in which the raw oil is first fed into a scrubbing zone andfrom there into two subsequent purification zones, in one of which theimpurities are volatilized and the volatilized impurities are passedinto the scrubbing zone to be scrubbed with the fresh raw oil fedthereinto so that the latter will absorbthe impurities and the raw oilthus containing an increased percentage of impurities is subjected inthe other purification zone to purification in which at least a part ofthe impurities are removed by neutralization or distillatron.

METHOD FOR REMOVING VOlLATllLE IMPURITIES FROM RAW OIL BY SCRUBBING ANDDISTILLATION WITH A STRKPPING GAS CROSS-REFERENCE TO RELATED APPLICATIONThis application is a continuation of application Ser. No. 524,405,filed Feb. 2, 1966, now abandoned.

The present invention relates to a method and apparatus for removingvolatilizable impurities from organic materials.

More particularly, the present invention is concerned with improvementsof conventional methods of treating organic materials generally, or morespecifically fats and oils destined for nutritional or technicalpurposes, by keeping the waste waters derived from injectioncondensation devices of steam jet vacuum apparatus or the like which areused, for instance, in deodorization arrangements, free of impurities.

Thus, the present invention is particularly concerned, however, withoutbeing limited thereto, with improvements of conventional methods andapparatus for the deodorization of, for instance, fish oils utilizinghydrogen gas as the inert gas. Furthermore, the present invention mayalso be advantageously applied to conventional processes of thepetroleum or mineral oil industry, according to which wax or petroleumjelly or also lubricating oil fractions are treated under a partialvacuum by blowing steam at elevated temperature through the material.

in carrying out such processes, considerable amounts of waste watersaccrue and, up to now, purification of these waste waters to such anextent that they may be easily disposed of frequently involved veryconsiderable expenses. The .elimination of such impurities from thewaste waters, or prevention of the introduction of such impurities intothe waste waters, represents a question of major technical andeconomical importance.

Arrangements were proposed which operate with surface condensationdevices at which volatilized impurities, carried along by thesteam-containing gaseous mixture derived in the purification of theorganic material, should condense. Furthermore, arrangements wereproposed in which either condensate is injected into the water vaporandimpurities: containing gaseous stream, or in which the vapors are washedwith fatty acids of the type contained in the original oil, fat or' thelike. These types of arrangements and processes are described, forinstance, in Seifen-Oele-Fettes Wachse No. 9, 1956, page 228; and alsoin German-published patent application DAS 1,133,489.

However, all of these methods and devices require that the vapors justbefore being released or condensedare contacted with condensatecontaining the same type of impurities as the organic aterial which isto be treated. Particularly if the material which is to be deodorizedcontains a proportion of easily volatilizable, low-boiling impurities,it might, and frequently will, occur that even at condensationtemperature the partial pressure of one or several of the impuritieswill be so high that the concentration of these impurities in thetreated vapors or the waste water derived therefrom still will be higherthan permissible.

It is therefore an object of the present invention to overcome theabove-discussed difficulties and disadvantages in the removal ofvolatilizable impurities from organic material, particularly fats, oils,waxes and the like.

It is another object of the present invention to provide a method andapparatus for the removal of volatilizable impurities from organicmaterial which will permit the release of a water vapor-containinggaseous mixture which is substantially free of, or contains onlyinsignificant amounts of the volatilizable impurities of the organicmaterial which is to be purified so that waste water formed bycondensation of these vapors will be sufficientpurity to be releasedwithout causing any difficulties.

It is a further object of the present invention to provide a method andapparatus for the purification of volatilizable impurities of anyorganic material which will result in waste waters of sufficient purityso that disposal thereof does not cause any difiiculties, and which canbe carried out in a simple and economical manner.

Other objects and advantages of the present invention will becomeapparent from a further reading of the description and of the appendedclaims.

With the above and other objects in view, the present inventioncontemplates in a method of purification of volatilizableimpurities-containing organic material, the steps of subjecting theorganic material to subatmospheric pressure sufficiently low to strip atleast a substantial portion of the volatilizable impurities, therebyforming a purified organic material and a gaseous mixture containingvolatilized impurities, and scrubbing the gaseous mixture withsuccessive portions of the organic material so as to withdraw at least asubstantial portion of the volatilized impurities from the gaseousmixture and incorporating the withdrawn portion in the successiveportions of the organic material thereby increasing the content ofvolatilizable impurities thereof, the thus-formed successive portions oforganic material of increased volatilizable impurities content servingas volatilizable impurities-containing raw material for subsequentpurification.

The present invention also includes in an apparatus for the purificationof volatilizable impurities-containing organic material, in combination,scrubbing means for scrubbing a gaseous mixture containing theimpurities in volatilized form with a liquid organic material containingthe impurities in volatilizable form, so as to increase theconcentration of the impurities in the liquid organic material and to atleast substantially decrease the concentration of the impurities in thegaseous mixture, withdrawal means for withdrawing the gaseous mixture ofat least substantially reduced impurities concentration from thescrubbing means; volatilizing means communicating with the scrubbingmeans for receiving the liquid of increased impurities concentrationformed in the scrubbing means, and for stripping at subatmosphericpressure at least a major portion of the volatilizable impuritiescontained in the liquid, thereby forming a gaseous mixture containingthe impurities in volatilized form and organic liquid material ofsubstantially reduced impurities content, conduit means for introducingthe gaseous mixture containing the impurities into the scrubbing means,introducing means for introducing liquid impurities-containing materialinto the scrubbing means, and recovery means for recovering from thevolatilizing means organic liquid material of substantially reducedimpurities content.

The prior art difficulties and disadvantages in the method of separatingvolatilized impurities which lend themselves to condensation from themixture of inert gas and water vapors such as are produced during thedeodorization and/or acid distillation of oils, fats, waxes and the likeunder a high degree of vacuum, are thus overcome according to thepresent invention by scrubbing such gaseous mixture with subsequentportions of the organic raw material from which the volatilizableimpurities are to be removed and which therefore will contain impuritiesof the same type as the condensable impurities contained in the watervapors or the gaseous mixture.

According to Raoults Law, the fraction by which the vapor pressure ofaliquid is lowered when a small amount of a nonvolatile substance isdissolved in it, is equal to the mole fraction of the solute, or, inother words, under equilibrium conditions, the partial pressure of onecomponent in the water vapors-containing gaseous mixture is proportionalto the mole fraction of the same component in the liquid phase. Thus, byscrubbing with the condensate formed of the vapors, which condensatecontains the volatilizable impurities in very high concentration, thescrubbing liquid, i.e. the condensate, will contain a high-mole fractionof the impurities. In contrast thereto, when using the liquid organicraw material, such as an oil, fat or the like, as the scrubbing liquid,the mole fraction of the impurities therein will be much lower, inasmuchas the concentration of volatilizable impurities in the liquid organicstarting material is considerably lower than in the condensate of thewater vapors formed in the steam jet vacuum apparatus or the like whichis used for stripping such impurities from the starting material.

Thus, in the case of oils and fats, the mole fraction of thesevolatilizable impurities in the raw oil or the like which is to bepurified will be of the magnitude of between 0.15 and 0.01, as comparedto a mole fraction of up to l in the condensate.

In a similar ratio, the partial pressure of the fatty acids in the watervapors withdrawn from the purification device is also reduced andconsequently also the proportion of fatty acids in the waste watersformed by condensation of the water vapors.

A further reduction of the fatty acid proportion in the waste water isachieved by using the raw oil or the like for scrubbing of thevolatilized fatty acid-containing vapors, due to the fact that generallythe solidification point of the raw oil or the like is considerablylower than the solidification point of the condensed fatty acids. Due tothis fact, it is possible to operate a scrubber in which the vapors arescrubbed with raw oil or other liquid organic material which is to bepurified, at a considerably lower temperature than a scrubber in whichcondensed fatty acids are used as the scrubbing liquid. Consequently, itis possible to operate at a lower temperature of the vapors orvapors-containing gaseous mixture, and this in turn will considerablyreduce the partial pressure of the fatty acids component and thus theresidual fatty acid content of the scrubbed water vapors which, uponcondensation form waste water.

In addition to the above-discussed advantage which permits a highlysignificant reduction in the residual fatty acid content of the wastewater, the use, in accordance with the present invention, of thestarting material, such as oil, as the scrubbing liquid will result in agreat procedural advantage, due to the fact that the condensedimpurities which are taken up by the starting material during thescrubbing can be separated therefrom in the same process step in whichthe major portion of the impurities initially contained in the startingmaterial are separated therefrom.

Generally, during the deodorization step, or the stripping ofimpurities, for instance in a steam-fed vacuum apparatus, only residualportions of the volatilizable impurities are separated from the organicmaterial such as an oil, fat, or wax, while the major portion of thesevolatilizable impurities is separated in a preceding process step. Forinstance, during the purification of oils, generally the free fatty acidcontent of the raw oil is reduced by treatment with alkali until only asmall residual portion of the free fatty acids is present in the oil.This residual portion is then stripped off to a large extent during thedeodorization, for instance in a conventional steam jet vacuumapparatus, and only this residual portion of the free fatty acids willeventually be found in the waste water of the deodorization apparatus.It then, in accordance with the present invention, the water vaporsemanating from the deodorization apparatus are washed with the raw oil,then the amount of free fatty acid in the raw oil will be increased bythe amount thereof which is taken up from the water vapors. Thisadditional amount of fatty acids will be removed during the alkalinedeacidification or other preliminary purification down to the sameresidual amount of free fatty acids which would be retained in the rawoil if the same had not been used for scrubbing of the water vapors andthus would not contain an increased amount of free fatty acids. Itfollows, that the refined product obtained in the alkalinedeacidification process will pass to the deodorizing apparatus with thesame amount or proportion of free fatty acids therein, irrespective ofwhether or not the raw oil has been used for scrubbing of the watervapors previously formed in the deodorization apparatus.

The present invention can be utilized in a similar manner in processeswherein the major portion of the volatilizable impurities is withdrawnnot by treatment with chemicals, such as treatment with lye, but by adistillation process which precedes the thus described volatilization orthe like. In the latter case, the additional amount of volatilizableimpurities which is taken up by the raw oil or the like during scrubbingof the water vapors derived from the deodorization apparatus will beremoved by distillation together with the initial volatilizableimpurities content of the raw oil, so that the residual amount ofvolatilizable impurities in the oil after the distillation process andprior to deodorization will be the same irrespective of whether thecontent of volatilizable impurities in the oil has been increased byusing the raw oil as a scrubbing liquid for the water vapors emanatingfrom the deodorization apparatus.

Furthermore, it is also possible to carry out the separation of themajor proportion of volatilizable impurities by distillation jointlywith deodorization of the oil or the like. According to this embodimentof the present invention, the major proportion of volatilizableimpurities is first separated from the water vapors-containing gaseousstream by means of a conventional condensing device. Thereafter, thewater vaporscontaining gaseous mixture is scrubbed with the raw oil orthe like and thereby, the residual portion of volatilized impuritiescontained in the water vapors, or at least a major proportion thereof,will be taken up by the raw oil.

According to the two last-described embodiments, wherein the majorproportion ofvolatilizable impurities is separated by distillation, afurther advantage will be achieved with respect to the method of thepresent invention.

It is conventional and generally necessary prior to treating materialswhich are sensitive to oxygen at substantially elevated temperatures, todegas such materials. This is carried out by subjecting the material atan elevated temperature to a partial vacuum while the same passesthrough a suitable, conventional column or the like. If, in accordancewith the present invention, the starting material is used for scrubbingthe water vapors-containing gas, then during such use of the startingmaterial the same will be simultaneously degassed so that a separatedegassing step prior to distillation or deodorization of the rawmaterial will no longer be required.

By proceeding according to the present invention, for deodorizating ordeacidifying fats and oils by distillation, the neutral oil, vaporscrubber device may be built ofiron, in contrast to a fatty acidcondenser or scrubbing device which is operated with condensate ofhigh-fatty fatty acid content, since at such high concentration of thefatty acids in the neutral oil the condenser or the scrubber would becorroded. This will not be the case if, in accordance with the presentinvention, the starting material is used as a scrubbing liquid and thusthe concentration of fatty acids in the scrubber will remain relativelylow.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG, 1 is a schematic illustration of an arrangement for the separationof volatilizable and condensable impurities during the purification ofoils, fats and the like;

FIG. 2 is a schematic illustration of an arrangement for the separationof volatilizable and condensable impurities during the purification ofoils and fats, which includes deacidification by distillation; and

FIG. 3 is a schematic illustration of an arrangement according to FIGS.1 and 2 wherein, however, the distillation of the fatty acids and thedeodorization are carried out in one and the same apparatus.

As seen in FIG. 1, the raw oil is passed from container 1 by way of pump2 and cooler 3 and then through nozzle 4 into scrubber 5. In cooler 3,the raw oil is cooled to a temperature which is only slightly above thesolidification point of the oil. The term raw oil is meant to denote thetype of volatilizable impurities containing organic material which maybe subjected to refining and which also serves as the scrubbing liquidfor the water vapors-containing gas emanating from the inert gas orsteam vacuum purification device.

Nozzle 4 serves for finely spraying the oil over a layer 6 of packing orfiller material which may consist of Raschig rings, Intalox bodies orthe like.

A second layer 7 of filler material is arranged in scrubber 5 abovenozzle 4 for the purpose of preventing the carrying-over of liquidparticles into the vacuum apparatus which communicates with scrubber 5at outlet 8.

Oil trickles through filler material layer 6 toward the bottom of thescrubber, while simultaneously the gas and vapor mixture emanating fromdeodorizer 9 is introduced into the bottom portion of the scrubber,passes through filler material layer 6 and gives up its fatty acidcontent to the neutral oil flowing downwardly from nozzle 4. The thusfatty acidcharged neutral oil collects at the bottom of washer 5 andpasses from there through conduit 10 into the next process step, namelythe refining apparatus 10.

It is sometimes desirable to use only a portion of the raw oil which isto be purified for trickling or otherwise passing through filler layer 6of scrubber 5. In this case, another portion of the raw oil which isconveyed by pump 2 may be passed through valve 11 directly into refiningapparatus 10. Furthermore, it may be desirable to circulate thescrubbing oil several times prior to introduction into refiningapparatus 10. For this purpose, a circulation pump 12 may be providedthrough which the oil from the bottom of scrubber 5 will be recirculatedto nozzle 4 by way ofcooler 3.

In refining stage or apparatus 10, the major proportion of the freefatty acids which initially were contained in the raw oil and/or whichwere introduced into the crude oil in scrubber 5 are removed. This isgenerally done in conventional manner by treatment with alkali and maybe followed by drying and treatment with bleaching earth fordecolorizing the oil. After passing through stage 10, the oil is pumpedby means of pump 13 into deodorizer 9 which may operate as a continuousdeodorizer or also in a batchwise manner. In deodorizer 9, the oil istreated with finely subdivided steam which is introduced into deodorizer9 as indicated by arrow 14. After such treatment has continued for therequired length of time, as well known to those skilled in the art, theresidual free fatty acid of the oil, and other distillable impurities,will be stripped from the oil into the vapor phase. These impurities,together with the vapors are then introduced into the bottom portion ofscrubber 5 and therein the impurities will be taken up to a very largeextent by the raw oil introduced through nozzle 4. After carrying outtreatment in deodorizer 9 for the required length of time, the thuspurified oil is withdrawn as indicated by arrow 15.

In accordance with the arrangement illustrated in FIG. 2, the raw oil isintroduced at 16 into the first treating stage 17 in which, by suitableconventional treatment, mucilaginous materials and other nondistillableimpurities are separated from the oil. The thus pretreated oil is thenpassed by means of pump 18 through cooler 19, in which the oil is againcooled to a temperature just above its solidification point, and fromthere to vapor scrubber 10. Vapor washer 20 is again provided with anupper layer 21 of filler material which prevents the carrying along ofdroplets of liquid into vacuum apparatus 22. The oil introduced intoscrubber 20 from cooler 19 is sprayed through nozzle 23 over a layer 24of filler material and will collect in the lower portion or sump ofscrubber 20. As described in connection with FIG. 1, it may be desirableto use only a portion of the raw oil for scrubbing of thevapors-containing gaseous mixture, and this can be achieved by utilizingvalve 25 for passing part of the raw oil directly to distillingapparatus 28. On the other hand, it may also be desirable to recirculatethe scrubbing oil several times through scrubber 20. This can beaccomplished by operation of circulating pump 26.

The oil which in scrubber 20 has absorbed free fatty acids from thewater vapors then passes through preheater 27 into distillationapparatus 28 in which the fatty-acids-containing oil is heated at a hightemperature while simultaneously being maintained under a high degree ofvacuum so that the distillable constituents, particularly impuritieswhich may be removed by distillation, will be removed from the oil. Ifdesirable, it is also possible to introduce steam into the distillationapparatus during operation of the same. The distillation apparatus, perse, is well known to those skilled in the art and may be operated in acontinuous or batchwise manner.

The vapors which are expelled from the oil pass through a fatty acidcondenser 29 which is illustrated in FIG. 2 as a direct condenser withcirculating fatty acid. In condenser 29, cooled fatty acid is sprayedthrough nozzle 30 over a layer 31 of conventional filler material,withdrawn at the bottom of condenser 29, passed into vessel 32 andwithdrawn therefrom at atmospheric pressure. The condensed portion ofthe fatty acid is thus withdrawn from vessel 32 while thestill-vaporized portion thereof is passed by means of circulating pump33 through fatty acid cooler 34 to nozzle 30 and is used again fortrickling through filler material layer 31. In filler material layer 31,the major portion of the free fatty acid which has been distilled off indistillation device 28 is condensed, with the exception of a residualamount which, corresponding to the partial pressure of the fatty acid incondenser 29 is still volatile at the prevailing temperature andsubatmospheric pressure. In order to prevent carrying along of liquiddroplets, a further layer 35 of filler material is provided in the upperportion of fatty acid condenser 29, and the vapors have to pass throughlayer 35. The oil is pumped by means of pump 36 from distillation device28 into the deodorizer 37 into which steam is introduced as indicated byarrow 38. Within deodorizer 37 which may be a conventional continuouslyor batchwise-operating apparatus, the residual free fatty acids or othervolatilizable impurities are stripped from the oil at elevatedtemperature and high vacuum. The stripped volatilized constituents ofthe oil leave the deodorizing apparatus through conduit 39. As indicatedby arrow 40, the thus purified oil is withdrawn from deodorizer 37. Thevapors which are withdrawn from fatty acid condenser 39 and deodorizer37 may be combined below scrubber 20 and will then be jointly scrubbedin scrubber 20 by means of the raw oil which is passed through theprepurification. The oil removes from the vapors the residual free fattyacid content and any other condensable constituents thereof.

Referring now to the arrangement illustrated in FIG. 3, it will be seenthat the distillation of the fatty acids and the deodorization arecarried out in a joint apparatus. Similar to what has been described inconnection with FIG. 2, the raw oil is introduced at 41 into apretreatment stage 42 and, after such pretreatment is passed by means ofpump 43 through cooler 44 into scrubber 45. Scrubber 45 is substantiallyconstructed in the same manner as the scrubbers in FIGS. 1 and 2. Theoil is evenly distributed on filler layer 47 by means of nozzle 46.Carrying along of liquid droplets into the vacuum apparatus is preventedby layer 48 of filler material which is arranged above nozzle 46. Thepretreated oil after passing through scrubber 45 leaves the same at thebottom portion thereof and passes through heat exchanger 49, in whichthe oil is heated, into a combined deacidification and deodorizingapparatus 50. In a manner similar to that described with respect toFIGS. 1 and 2, valve 51 and pump 52 are provided in the event that onlya portion of the raw oil is to be passed through scrubber 45, or if theoil should be recirculated several times through scrubber 45. In thedeodorizing and deacidification apparatus 50, the oil is treated atelevated temperature with steam introduced at 53, and the thus treatedand purified oil leaves the combined deodorizer and deacidifier asindicated by arrow 54.

The vapors which were thus enriched with fatty acids and other volatileimpurities leave deodorizer 50 at the upper end thereof and areintroduced into fatty acid condenser 55, the latter being operated withcirculating cooled fatty acids as described in connection with FIG. 2.The cooled fatty acids are finely distributed over layer 57 of fillermaterial by being sprayed onto the same through nozzle 56. The fattyacids then are withdrawn from the bottom of condenser 55 and collectedin container 58 from which, as indicated by arrow 59, condensed fattyacid is withdrawn at atmospheric pressure, and a portion thereoftaken upby pump 60, The portion of fatty acid which passes through pump 60 isthen conveyed through cooler 61 back to nozzle 56 for distribution onlayer 57 of filler material.

The vapors which are thus freed of the major portion of the fatty acidpass through layer 62 of filler material in order to prevent carryingalong of droplets of liquid and then leave the fatty acid condenser atthe top thereof for introduction into the bottom portion of scrubber 45,wherein, within layer 47 of filler material, the last traces of fattyacids and other volatilizable impurities are removed from the vapors incontact with the pretreated raw oil which has been sprayed throughnozzle 46.

It is rather important, and thus will be mentioned again, that thescrubber in which the vapors are washed with raw oil may in nearly allcases be built ofiron, while the fatty acid condensers must have atleast inner surfaces of rustproof steel, in view of the high degreeofchemical reactivity of the free fatty acids.

The following examples, which will make reference to the drawing, aregiven as illustrative only, without, however, limiting the invention tothe specific details of the examples.

EXAMPLE 1 Soybean or peanut oil may be processed in the arrangementillustrated in FIG. 1, in the following manner;

The oil in storage container 1 may have a content of l percent of freefatty acids. conventionally, i.e. without the scrubbing of vapors inaccordance with the present invention, the free fatty acid content isreduced in refining stage 10, in conventional manner, for instance bytreatment with lye, to about 0.1 percent. Upon deodorization indeodorizer 9, the fatty acid content is further reduced to about 0.03percent so that an amount offatty acid equal to about 0.07 percent ofthe amount of oil which is to be purified will pass with the vapors intothe vacuum apparatus and thus into the waste water. Devices without thevapor scrubber according to the present invention show in the wastewater of the vacuum apparatus a contamination equal to between about 60and 100 ppm. of fatty acid. By interposition of vapor scrubber 5according to the present invention, the major portion of the 0.07percent fatty acid which were stripped in deodorizer 9 will be taken upby the raw material such as soybean oil or peanut oil which is used asthe scrubbing liquid. Thereby, the fatty acid content of the raw oilrises from about 1.0 percent to about 1.06 percent. For the operation inrefining stage 10 in which the raw oil is treated with lye, it isimmaterial whether the free fatty acid content of the oil is 1.0 or 1.06percent. In either case, the oil will leave refining stage 10 with afree fatty acid content of 0.01 percent.

Consequently, of the 0.07 percent of fatty acid, only about 0.01 percentor even less will pass into the vacuum apparatus and into the wastewater so that the contamination of the waste water will be reduced toless than ppm. which degree of contamination is generally permissible.

EXAMPLE 2 The process as illustrated in FIG. 2 is particularly suitablefor treating palm oil containing between 5 and 12 percent fatty acid. Inthe deacidification stage 28, the fatty acid content is reduced by steamdistillation to between about 0.5 and 0.3 percent. The main portion ofthe driven-off fatty acid is condensed in condenser 30, as described inconnection with FIG. 2. The vapors leaving condenser 30, however, maystill contain considerable quantities of fatty acid. For instance at acondensation temperature of 40 C. and subatmospheric pressure ofmm./llg., the vapors may contain capric acid with eight carbon atoms,which cannot be condensed under these conditions, in an amount of about6.5 grams per kilogram of steam.

The fatty acid content of the palm oil is reduced in deodorizer 37 frombetween 0.5 and 0.3 percent to about 0.03 percent. The vapors leavingdeodorizer 37 and containing between 0.47 and 0.27 percent fatty acidsare introduced jointly with the vapors from the fatty acids condenser 30into scrubber 20 wherein the vapors are washed with raw oil so that thefatty acid content of the raw oil used for scrubbing the vapors willincrease from between 5 and 12 percent to between 5.47 and 12.47 percentor between 5.27 and 12.27 percent.

The amount of fatty acid which is contained in the vapors leavingscrubber 20 depends on the vapor pressure of the individual fatty acid,reduced in the ratio of mole fraction of fatty acid and neutral oil inthe scrubbing liquid. This reduction in the amount of fatty acid in thevapors leaving scrubber 20 as compared with the vapors leaving condenser30 can be calculated, for instance for capric acid (C at 40 C., 25mm./Hg. pressure and 5 percent free fatty acid in the raw oil, in thefollowing manner.

Whereby:

Z (The fatty acids content ofthe raw material) 5 percent Z (The neutraloil content of the raw material) percent M (The molecular weight oftheneutral oil) 870 M, (The molecular weight of capric acid) 144 Theabove-mentioned proportion of capric acid, namely 6.5 g./kg. water vaporis thus reduced to 6.5X0.032, or to about 0.2 g. capric acid perkilogram water vapor, so that only generally permissible traces of fattyacid will be found in the waste waters.

EXAMPLE 3 The process in accordance with FIG. 3 of the drawing isparticularly suitable for working up coconut oil and palm kernel oilcontaining between 1 and 10 percent fatty acids. These oils are firsttreated in a pretreating stage 42, for instance with phosphoric acid andFuller's earth, for removing mulcilaginous substances. Then, the entirefatty acid content is stripped in one stage, namely in deodorizer 50,and the stripped fatty acid is condensed in fatty acid condenser 55.Since, as described in example 2, fatty acid condenser 55 is not capableof completely condensing the entire fatty acid content, the residualamount of fatty acid in the vapors is further reduced in scrubber 45 inthe ratio of the mole fractions.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofoil and the like purification arrangements differing from the typesdescribed above.

While the invention has been illustrated and described as embodied in anoil and the like purifying arrangement including a device for scrubbingvolatile impurities-containing vapors with the raw oil or the like, itis not intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence ofthe followingclaims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A method for processing a raw oil containing volatilizable impuritiesincluding fatty acids, said oil being selected from the group consistingof liquid raw vegetable, mineral and fish raw oils, comprising the stepsof removing from the raw oil a portion of said impurities to yield anoil'product having a reduced volatilizable impurity content, deodorizingsaid oil product with an inert gas under vacuum in a deodorizer forallowing volatilizable impurities still present in said oil productafter the step of removing to be stripped out of said oil product bysaid inert gas, scrubbing the inert gas resulting from the step ofdeodorizing with raw oil for allowing said inert gas to give up to saidraw oil the impurities acquired by said inert gas in the step ofdeodorizing, and passing the raw oil used in the step of scrubbing tothe step of removing.

2. A method as claimed in claim 1, wherein said inert gas is steam.

3. A method as claimed in claim 2, wherein said oil is a vegetable oil.

4. A method as claimed in claim 3, wherein said vegetable oil isselected from the group consisting of soybean oil, peanut oil, palm oil,coconut oil and palm kernel oil.

5. A method for processing a raw oil containing volatilizableimpurities, comprising the steps of distilling from the raw oil aportion of said impurities to yield a volatilized impurity product andan oil product having a reduced volatilizable impurity content,partially condensing said volatilized impurity product by sprayingthereinto said volatilized impurity product in a cooled condensed state,there remaining after the step of partially condensing a portion of saidvolatilized impurity product still in the volatilized state, deodorizingsaid oil product with an inert gas under vacuum in a deodorizer forallowing volatilizable impurities still present in said oil productafter the step of removing to be stripped out of said oil product bysaid inert gas, scrubbing the inert gas resulting from the step ofdeodorizing and said volatilized impurity product still in thevolatilized state after the step of partially condensing with raw oilfor allowing said inert gas to give up to said raw oil the impuritiesacquired by said inert gas in the step of deodorizing and for furthercondensing said volatilized impurity product, and passing the raw oilused in the step of scrubbing to the step of distilling.

6. A method as claimed in claim 5, wherein said inert gas is steam.

7. A method as claimed in claim 6, wherein said volatilizable impuritiesinclude fatty acids, said oil being selected from the group consistingof liquid raw vegetable, mineral and fish raw oils.

8. A method as claimed in claim 7, wherein said oil is a vegetable oil.

9. A method as claimed in claim 8, wherein said vegetable oil is palmoil.

10. A method as claimed in claim 9, wherein said palm oil containscapric acid.

11. A method for processing a raw oil containing volatilizableimpurities, comprising the steps of distilling and deodorizing said rawoil with an inert gas to yield an oil product substantially free of saidvolatizable impurities and for allowing said volatilizable impurities tobe stripped out of said raw oil by said inert gas, partially condensingthe volatilized impurities in said inert gas following the step ofdistilling and deodorizing by spraying thereinto cooled condensedvolatilizable impurities previously condensed from the volatilizedimpurities in said inert gas following the step of distilling anddeodorizing, there remaining after the step of partially condensing aportion of the volatilized impurities still in the volatilized state insaid inert gas, scrubbing the inert gas following the step of partiallycondensing with raw oil for allowing said inert gas to give up to saidraw oil the volatilized impurities still in the inert gas following thestep of partially condensing, and passing the raw oil used in the stepof scrubbing to the step of distilling and deodorizing.

12. A method as claimed in claim 11, wherein said inert gas is steam.

13. A method as claimed in claim 12, wherein said volatilizableimpurities include fatty acids, said oil being selected from the groupconsisting of liquid raw vegetable, mineral and fish raw oils.

14. A method as claimed in claim 13, wherein said oil is a vegetableoil.

15. A method as claimed in claim 14, wherein said vegetable oil isselected from the group consisting of coconut oil and palm kernel oil.

16. A method as claimed in claim 15, wherein said vegetable oil containsbetween 1 and 10 percent fatty acids.

2. A method as claimed in claim 1, wherein said inert gas is steam.
 3. Amethod as claimed in claim 2, wherein said oil is a vegetable oil.
 4. Amethod as claimed in claim 3, wherein said vegetable oil is selectedfrom the gRoup consisting of soybean oil, peanut oil, palm oil, coconutoil and palm kernel oil.
 5. A method for processing a raw oil containingvolatilizable impurities, comprising the steps of distilling from theraw oil a portion of said impurities to yield a volatilized impurityproduct and an oil product having a reduced volatilizable impuritycontent, partially condensing said volatilized impurity product byspraying thereinto said volatilized impurity product in a cooledcondensed state, there remaining after the step of partially condensinga portion of said volatilized impurity product still in the volatilizedstate, deodorizing said oil product with an inert gas under vacuum in adeodorizer for allowing volatilizable impurities still present in saidoil product after the step of removing to be stripped out of said oilproduct by said inert gas, scrubbing the inert gas resulting from thestep of deodorizing and said volatilized impurity product still in thevolatilized state after the step of partially condensing with raw oilfor allowing said inert gas to give up to said raw oil the impuritiesacquired by said inert gas in the step of deodorizing and for furthercondensing said volatilized impurity product, and passing the raw oilused in the step of scrubbing to the step of distilling.
 6. A method asclaimed in claim 5, wherein said inert gas is steam.
 7. A method asclaimed in claim 6, wherein said volatilizable impurities include fattyacids, said oil being selected from the group consisting of liquid rawvegetable, mineral and fish raw oils.
 8. A method as claimed in claim 7,wherein said oil is a vegetable oil.
 9. A method as claimed in claim 8,wherein said vegetable oil is palm oil.
 10. A method as claimed in claim9, wherein said palm oil contains capric acid.
 11. A method forprocessing a raw oil containing volatilizable impurities, comprising thesteps of distilling and deodorizing said raw oil with an inert gas toyield an oil product substantially free of said volatizable impuritiesand for allowing said volatilizable impurities to be stripped out ofsaid raw oil by said inert gas, partially condensing the volatilizedimpurities in said inert gas following the step of distilling anddeodorizing by spraying thereinto cooled condensed volatilizableimpurities previously condensed from the volatilized impurities in saidinert gas following the step of distilling and deodorizing, thereremaining after the step of partially condensing a portion of thevolatilized impurities still in the volatilized state in said inert gas,scrubbing the inert gas following the step of partially condensing withraw oil for allowing said inert gas to give up to said raw oil thevolatilized impurities still in the inert gas following the step ofpartially condensing, and passing the raw oil used in the step ofscrubbing to the step of distilling and deodorizing.
 12. A method asclaimed in claim 11, wherein said inert gas is steam.
 13. A method asclaimed in claim 12, wherein said volatilizable impurities include fattyacids, said oil being selected from the group consisting of liquid rawvegetable, mineral and fish raw oils.
 14. A method as claimed in claim13, wherein said oil is a vegetable oil.
 15. A method as claimed inclaim 14, wherein said vegetable oil is selected from the groupconsisting of coconut oil and palm kernel oil.
 16. A method as claimedin claim 15, wherein said vegetable oil contains between 1 and 10percent fatty acids.